1. Technician License Course Chapter 3 Operating Station Equipment Power Supplies and Batteries Handheld Transceivers RF Interference (RFI)

2. Power Supplies Most modern radio equipment runs off 12 volts DC Household current is 120 volts AC Power supplies convert 120 volts AC to 12 volts DC –13.8 volts DC is the common voltage you will see –This is the charging voltage for motorized vehicles

3. Power Supply Ratings Voltage and Current Continuous duty – how much current can be supplied over the long term Intermittent duty – how much surge current can be supplied over the short term Regulation – how well the power supply can handle rapid current changes

4. Types of Power Supplies Linear –Transformers –Heavy (physically) –Heavy duty current –Expensive Switching –Electronics instead of transformers –Light weight and small –Not as robust –Less expensive

5. Inverters and Generators Inverters convert DC into AC –Square, triangle, sine-wave inverters Generators create AC –Gas powered –Various voltage and current ratings –Special precautions

6. Batteries Create current through a chemical reaction –Made up of individual cells (approximately 1.5 volts per cell) connected in series or parallel Battery types –Disposable –Rechargeable –Storage Power capabilities rated in Ampere-hours –Amps X time

7. Battery Charging Some batteries can be recharged, some cannot Use the proper charger for the battery being charged Batteries will wear out over time Best if batteries are maintained fully charged –Over-charging will cause heating and could damage the battery Some batteries (lead-acid) will release toxic fumes during charging so require ventilation

8. Handheld Transceivers Single, dual and multi-band versions (with increasing cost and complexity) –Some have expanded receiver coverage (wide- band receive) Very portable and self-contained –Internal microphone and speaker –Rubber duck antenna –Battery powered

9. Nice to have handheld accessories Extra battery packs Drop-in, fast charger Extended antenna External microphone and speaker Headset

10. Radio Frequency Interference (RFI) Un-wanted, un-intentional signals from some electronic device that interferes with radio wave reception You can prevent creating RFI by operating your transmitting equipment properly

11. RFI Mitigation Filters –Filters attenuate (reduce) interfering signals – but do not totally eliminate them High –generally on the receive side Low – generally on the transmit side Band-pass – used within most radio equipment

12. Types of RFI Direct detection – offending signals get into the electronics circuits to cause interference Overload – strong signal that overwhelms the weaker, wanted signal Harmonics – even multiples of the offending signal that coincided with the wanted signal

13. Cable TV Interference Usually the result of broken shielding somewhere in the cable –Loose connections –Broken connections –Corroded connections Usually solved by proper cable maintenance by cable supplier –If the subscriber is a legitimate subscriber

14. Noise Sources Electrical arcs (motors, thermostats, electric fences, neon signs) Power lines Motor vehicle ignitions Motor vehicle alternators Switching power supplies Computers, networks, and TV sets

15. Dealing with RFI Make sure you operate your equipment properly Eliminate interference in your own home first

16. Dealing with RFI Take interference complaints seriously Make sure that you’re really not the cause (demonstrate that you don’t interfere within your own home) Offer to help eliminate the RFI, even if you are not at fault Consult ARRL RFI Resources for help and assistance

17. What the Rules Say RFI from and to unlicensed devices is the responsibility of the users of such devices Bottom line – if your station is operating properly, you are protected against interference complaints BUT – be a good neighbor because they may (probably) not be familiar with Part 15 rules and regulations

18. Review Questions T4C06 through 10, T5A05, T0A10 and 11 T7A03, T9B07 and 08, T9A04 T5A07 and 07, T3D02, 03, 07, and 11, T5D01 through 04, 06 through 10, T7A05, T9B03

19. Next Time Communicating with other hams –Making Contacts Read 4-1 through 4-19